Tank of liquid able to be heated

ABSTRACT

Tank ( 1 ) comprising a chamber ( 2 ) to receive liquid, a shell ( 3 ) surrounding the chamber ( 2 ) and a resistive electric element ( 13 ) that can be positioned inside the chamber ( 2 ). The tank comprises two orifices ( 5, 6 ) facing each other, one of them ( 5 ) formed in the chamber ( 2 ) and the other ( 6 ) in the shell ( 3 ) and connected by a casing body ( 7 ) comprising a bottom ( 8 ) and a peripheral side wall ( 9 ), the casing body ( 7 ) and the chamber are made of a synthetic material, the casing body ( 7 ), of which the bottom ( 8 ) is holed, forms a connecting sleeve connecting said orifices ( 5, 6 ) to one another, the hole in the bottom ( 8 ) is externally bordered by a rim to form a tubular projection ( 12 ) inserted into the orifice ( 5 ) of the chamber ( 2 ), and the resistive electric element ( 13 ) takes the form of an elongate body fitted with a seal configured so that, in collaboration with the resistive electric element ( 3 ), it seals the hole.

The invention relates to a tank for liquid able to be heated.

It relates more particularly to a tank for liquid comprising a liquid receiving chamber, a shell surrounding the chamber and at least one resistive electrical element that can be positioned at least partially inside the chamber.

Such a tank for liquid is known. In order to heat the contents of such a tank it is known practice to employ one or more resistive electrical elements at least partially immersed in the chamber as described, for example, in document DE8428132 or FR2005517. The difficulty however lies in attaching the resistive electrical element to the chamber with a view to simple and rapid assembly without detriment to ease of maintenance.

An object of the invention is therefore to propose a tank for liquid of the aforementioned type of the design of which allows ease of placement and of maintenance of the resistive electrical element or elements with which said tank is equipped.

To that end, the subject matter of the invention is a tank for liquid comprising:

-   -   a liquid receiving chamber,     -   a shell at least partially surrounding the chamber, and     -   at least one resistive electric element that can be positioned         at least partially inside the chamber,         characterized in that the tank comprises, for receiving the or         at least one of the electric resistive elements, two orifices         facing each other, one of them, being formed in the chamber and         the other being formed in the shell, in that the orifices are         connected by a casing body comprising a bottom and a peripheral         side wall, in that the casing body and the chamber are made of a         synthetic material, in that the casing body, the bottom of which         is holed, forms a connecting sleeve connecting said orifices to         one another, in that the hole in the bottom of the casing body         is externally bordered by a rim forming a tubular projection         inserted into the orifice of the chamber, and in that the         resistive electrical element, which can be positioned inside the         casing body so that it is coaxial with the hole in the bottom of         the casing body in order to project into the chamber via said         hole, takes the form of an elongate body fitted with a seal         slipped over the resistive electrical element, this seal, in         fluid tight contact with the resistive electrical element, being         configured so that it, in collaboration with the resistive         electrical element, seals the hole in the bottom of the casing         body in a fluid tight manner when the resistive electrical         element is in place inserted into said hole.

The use of a casing body and the fact that this casing body and the chamber are made from a synthetic material allow easy, reliable and rapid fitting of the resistive electrical element without detriment to ease of removal thereof. The overall design allows the resistive electrical element to be fitted and removed simply by sliding the resistive electrical element into the casing body without detriment to the reliability of the sealing.

The seal is slipped over the resistive electrical element. The fact that the seal is slipped over the resistive electrical element, which is to say the fact that the resistive electrical element is passed through at least one through-passage in the seal, allows the seal to be fitted and removed easily, making maintenance on such a tank easier.

According to one embodiment of the invention, the seal takes the form of an elastically deformable block equipped with at least two through-passages, said block being preferably equipped with annular bulges on its periphery surrounding said passages.

According to one embodiment of the invention, insulation is positioned between the chamber and the shell and surrounds the casing body. The presence of the casing body thus allows the orifices in the tank to be isolated from the insulation without detriment to the simplicity of fitting of the insulation.

According to one embodiment of the invention, the peripheral side wall of the casing body is equipped with an external peripheral flange positioned bearing against that part of the internal or external surface of the shell that surrounds the hole in the shell.

The flange may collaborate with the bottom of the casing in order to act as a spacer able to keep the tank at a predetermined distance from the shell.

According to one embodiment, the casing body is fixed to the chamber by welding. This simplifies implementation. As an alternative, a sealed attachment may be envisioned.

According to one embodiment of the invention, the tubular projection of the casing body, which projection is inserted into the orifice in the chamber, comprises at least one, preferably at least two thimbles open towards the inside of the casing body, each thimble being produced as one piece with the casing body. This arrangement allows electrical and/or electronic equipment able to supply data relating to the characteristics of the liquid contained inside the tank to be installed easily while avoiding any contact between the electrical and/or electronic equipment and the contents of the chamber.

According to one embodiment of the invention, the tank comprises a temperature probe that can be positioned inside the or one of the thimbles.

According to one embodiment of the invention, the tank comprises a fixing piece for fixing the resistive electrical element to the casing body, this fixing piece being able to be slipped over the resistive electrical element after the seal and being able to be coupled by screw-fastening members to the casing body, this casing body comprising at least one screw-fastening well produced as one piece with said body. This arrangement renders the seal captive.

As a preference, when the fixing piece used for fixing the resistive electrical element to the casing body is in position coupled to the casing body, it is positioned some distance from the seal.

According to one embodiment of the invention, the orifice in the shell is formed in a depression of the shell and the tank comprises a cap for closing the casing body which is housed inside said depression. The resistive electrical element is thus perfectly integrated into the tank.

According to one embodiment of the invention, the elongate body of the or at least one of the resistive electrical elements is a hairpin tubular body inside which there are housed a resistive wire and at least one hot-melt component, the ends of the hairpin which are produced in the form of two parallel branches each being equipped with an electrical connector via which the seal is slipped over said branches.

According to one embodiment of the invention, the tank is equipped with an orifice for filling the tank with liquid, this filling orifice being equipped with a connection piece for connecting to the tank, this connection piece being fitted with a vent, an overflow orifice and with an additional orifice acting as an overflow orifice or as a vent depending on the level to which the tank is filled.

The creation of a multifunctional connecting piece once again facilitates the manufacture and maintenance of the tank. This connecting piece may notably prevent any mixing of the contents of the tank with the network from which the filling fluid is taken during the filling step.

According to one embodiment, the vent, the overflow orifice and the additional orifice are positioned at different levels on the tank and the additional orifice is positioned at a level that is intermediate between the levels occupied by the vent and by the overflow orifice.

Another subject matter of the invention is a method for manufacturing a tank for liquid of the aforementioned type, said liquid tank comprising a liquid receiving chamber, a shell surrounding the chamber and at least one resistive electrical element equipped with a seal and which can be positioned at least partly inside the chamber, characterized in that, with the tank comprising, to receive the or at least one of the resistive electrical elements, two orifices facing one another, one of them formed in the chamber and the other in the shell, said method comprises a step of positioning a casing body in a position in which the casing body forms a connecting sleeve connecting the orifices of the chamber and of the shell to one another, the chamber and the casing body being made of a synthetic material, this casing body having a peripheral side wall and a holed bottom where the hole in the bottom of the casing body is externally bordered by a rim to form a tubular projection inserted into the orifice in the chamber when the casing body is in position in said position, and a step of positioning the resistive electric element inside the casing body coaxial with the hole in the bottom of the casing body so as to project via the hole into the chamber, the seal, with which the resistive electrical element is in bearing sealed contact, being configured so that in collaboration with said resistive electrical element, it seals the hole in the bottom of the casing body in a fluid tight manner when the resistive electrical element is in position inserted in said hole in the casing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be clearly understood from reading the following description of exemplary embodiments, with reference to the attached drawings, in which:

FIG. 1 depicts a schematic view, showing a normally hidden detail, of a tank for liquid according to the invention;

FIG. 2 depicts a partial view in section of a tank with a resistive electrical element mounted on the tank;

FIG. 3 depicts a partial perspective view of a tank, viewed in the region of the resistive electrical element, with the components shown in exploded view;

FIG. 4 depicts a view in cross section of a casing body; and

FIG. 5 depicts a view of the inside of a casing body;

FIG. 6 depicts an embodiment variant whereby a seal is preassembled on a casing body, when the casing body has not yet been assembled with an assembly comprising a chamber and a shell;

FIG. 7 depicts a view of FIG. 6 once the casing body has been engaged in said assembly which comprises the chamber and the shell so that the seal is compressed between the chamber and the casing body;

FIG. 8 depicts an exploded partial perspective view of the components of the casing body and of the associated resistive electrical element;

FIG. 9 depicts a partial view in cross section of the casing body and of the associated resistive electrical element of FIG. 8 .

The liquid tank 1, as depicted in FIG. 1 , can be used as a tank, notably in the case of an installation for producing domestic hot water. This liquid tank 1 comprises a liquid receiving chamber 2 made of a synthetic material, particularly a polyolefin material such as polypropylene.

This chamber 2 comprises at least one liquid inlet and/or outlet for filling and emptying the chamber 2. This chamber 2 comprises a shell 3 at least partially surrounding the chamber 2. This shell 3 may for example be formed of a body inside which the chamber can be at least partially housed, and of a lid for closing the body. This shell 3 is generally made of a synthetic material, particularly a polyolefin material, such as polypropylene, as in the example depicted.

The tank 1 further comprises one or more resistive electrical element(s) 13 that can be positioned at least partially inside the chamber 2. In the example depicted, the tank 1 comprises a single resistive electrical element 13 but could, equivalently, have comprised two or more of these, said resistive elements in that case being positioned at different levels within the chamber 2.

In order to house a resistive electrical element 13 inside the chamber 2, the tank 1 comprises two orifices 5, 6 formed facing one another, one of them, depicted as 5 in the figures, formed in the chamber 2 and the other, depicted as 6 in the figures, formed in the shell 3. These orifices 5 and 6 are connected by a casing body 7. This casing body 7 is preferably a molded synthetic component, particularly made of polyolefin, such as polypropylene.

The casing body 7, of cylindrical overall shape, comprises a bottom 8 and a peripheral side wall 9 adjoining the bottom. This peripheral side wall 9 delimits, on the opposite side to the bottom 8, an opening via which the resistive electrical element 13 can be inserted into the casing body 7. The bottom 8 of the casing body 7 is holed. The hole 10 in the bottom 8 of the casing body 7 is externally bordered by a rim 11 so as to form a tubular projection 12 that can be inserted into the orifice 5 of the chamber 2 until it projects into the chamber 2.

The resistive electrical element 13 itself takes the form of an elongate body 131 equipped with a seal 14. In the example depicted, the elongate body 131 of the resistive electrical element is a hairpin tubular body inside which there are housed a resistive wire 26 and at least one hot-melt component 27. The ends of the hairpin, which are produced in the form of two parallel branches, are each equipped with an electrical connector 24 by means of which the seal 14 is slipped onto the branches. The electrical connectors 24 are then connected to a control unit which will not be described in detail because it is well known to those skilled in the art.

The seal 14 is an elastically deformable block, preferably made of silicone. This seal 14 is equipped with two through-holes 141 so that it can be slipped over the ends of the hairpin that makes up the resistive electrical element 13. This block is preferably equipped with annular bulges 142 on its periphery surrounding the passages 141. The seal 14 when in place positioned on the resistive electrical element 13 is in sealed bearing contact with the resistive electrical element 13. The resistive electrical element 13 for its part can be positioned inside the casing body 7 coaxially with respect to the hole 10 in the bottom 8 of the casing body 7 so as to project, via said hole 10, into the chamber 2. This resistive electrical element and its seal 14 can thus be moved by sliding inside the casing body 7 into a position in which the seal 14, in collaboration with the resistive electrical element 13, seals in a fluid tight manner the hole 10 in the bottom 8 of the casing body 7.

The resistive electrical element 13 is therefore introduced via the opening in the casing body 7 into the casing body. It then passes through the casing body 7 to project from this casing body at the hole 10 in the bottom 8 of the casing body and to penetrate to a greater or lesser extent into the chamber 2. In this position, the seal 14 is positioned, particularly forcibly pushed into the tubular projection 12, as illustrated in FIG. 2 , and therefore, in collaboration with the resistive electrical element 13 seals said hole 10 in the bottom 8.

For improved fitting, the tank 1 comprises a fixing piece 20 for fixing the resistive electrical element 13 to the piercing body 7. This fixing piece 20 can be slipped over the resistive electrical element 13 after the seal 14 and can be coupled by screw-fastening to the casing body 7. When coupled to the casing body 7, the fixing piece 20 that fixes the resistive electrical element 13 to the casing body 7 is positioned away from the seal 14. Thus, the seal 14 is not compressed by said fixing piece 20 although this fixing piece 20 renders the seal captive against loss. To this end, the casing body 7 comprises at least one and, in this instance four, screw-fastening wells 21 produced as one piece with said body 7. Each screw-fastening well forms a self-tappable or tapped housing. This fixing piece in this instance takes the form of a mounting plate equipped with two through-passages through which the ends of the hairpin that constitutes the resistive electrical element can pass, and with two holed lugs each able to accept a screw-fastening member 34 such as a screw. Said holed lugs are arranged respectively in register with a screw-fastening well of the casing body when the fixing piece 20 is in position in the casing body so as to allow screws to be screwed into said wells.

In the examples depicted, the orifice 6 in the shell 3 is formed in a depression 22 of the shell 3 and the tank 1 comprises a closure cap 23 for closing the casing body 7 and housed inside said depression 22. This cap may be clip-fastened or screw-fastened to the casing body.

In the examples depicted, it is necessary to be able to take the temperature of the liquid. To this end, the tubular projection 12 of the casing body 7 which projection is inserted into the orifice 5 of the chamber 2 comprises a first thimble open towards the inside of the casing body 7, this thimble 171 being produced as one piece with the casing body 7. A temperature probe 18 can be positioned inside this first thimble 171.

The tubular projection 12 comprises a second thimble 172 produced in a similar way to the first thimble 171. A cutoff thermostat 19 can be positioned inside this second thimble. A component 25 of the tongue type may be attached to the casing body at the thimbles in order to hold the temperature probe and the cutoff thermostat in their respective housings formed by the thimbles.

In one embodiment of the invention, the casing body 7 is, in the position in which it forms a connecting sleeve connecting the orifice 5 of the chamber 2 and the orifice 6 of the shell 3, permanently fixed to the chamber by welding. In one particular embodiment, this welding is achieved by preheating the chamber 2 and the tubular projection 12 before assembling them with mechanical pressure. Other embodiments using welding may be envisioned.

The chamber thus preequipped with its casing body 7 can be positioned inside the shell 3 as far as a position in which the casing body 7 is positioned level with the orifice 6 of the shell 3 and is inserted at least partially into said orifice as illustrated in FIG. 1 . In this position, the orifices 5 of the chamber 2 and 6 of the shell 3 are connected by the casing body 7 which forms a sleeve connecting said orifices. In order to maintain a controlled and defined separation between the shell and the chamber at the casing body, the peripheral side wall 9 of the casing body 7 is equipped with an external peripheral flange 16. This flange 16 is positioned bearing against that part of the internal surface of the shell 3 that surrounds the orifice 6 of the shell 3 when the casing body is in position between the orifices 5 of the chamber 2 and 6 of the shell 3. Thus, the flange, in collaboration with the bottom of the casing body, forms a spacer maintaining a predefined distance between the chamber 2 and the shell 3.

To improve assembly, insulation 15, such as an expanded foam, may be positioned between the chamber 2 and the shell 3 and surround the casing body 7. This insulation 15 is fitted once the chamber 2 has been introduced into the shell 3 and the casing body has been positioned between the two orifices so that the casing body prevents any ingress of insulation 15 into the chamber 2 and prevents any insulation from leaving the shell 3.

To allow manufacture of a tank as described hereinabove, the procedure is as follows: the casing body is preattached by welding to the chamber 2 at the orifice 5 of the chamber so that the tubular projection 12 of the casing body projects from the orifice 5 of the chamber towards the inside of the chamber. The chamber 2 is introduced into the shell 3 as far as a position in which the orifices 5 of the chamber and 6 of the shell 3 face one another so as to allow the casing body to be partially inserted at its open end into the orifice 6 of the shell 3 as far as a position in which the flange 16 bears against the interior surface of the shell surrounding the orifice 6 of the shell 3. In this position, the insulation 15 can be introduced between the shell and the chamber. The casing body thus also acts as a guide to assist with the positioning of the chamber inside the shell 3.

Once the addition of the insulation 15 is complete, the shell 3 can be closed. The resistive electrical element 13 can be fitted into and removed from the chamber 2 at any time. To fit, it is sufficient to introduce the resistive electrical element 13 via the orifice 6 in the shell 3 into the casing body and then continue to move the resistive electrical element 13 in the casing body 7 until it projects from the tubular projection 12 of the casing body 7. The resistive electrical element 13 has been prefitted with a seal 14 which has been slipped over the resistive electrical element before the resistive electrical element is positioned in the chamber. The sliding movement of the resistive electrical elements towards the inside of the chamber 2 is therefore continued until the seal 14 is fitted into the tubular projection 12 of the casing body 7. All that is then required is to screw in the fixing piece 20 and the cap 23 to complete the fitting. To remove the resistive electrical element, the operations are performed in reverse, the resistive electrical element being extracted simply by pulling on said resistive element. This results in ease of maintenance of the assembly.

As a variant, the casing body 7 may be fixed to (assembled with) the chamber 2 by a joint. Thus, the description of the invention also applies to instances in which the casing is fixed to the chamber by a seal rather than by welding.

In particular, as illustrated in FIGS. 6 and 7 , provision may be made for an annular seal 28, for example of L-section, to be premounted on a smaller-diameter end portion of the tubular projection 12. When the casing body 7 is assembled with the chamber 2 by being engaged in the orifice 5 in the chamber (tank), the pre-mounted seal 28 is pushed onto the larger-diameter part of the tubular projection 12, thus being compressed between the chamber 2 and the casing body 7 during assembly.

The example depicted in FIGS. 8 and 9 similarly comprises a seal 28 slipped over the tubular projection 12. In this embodiment, the casing body 7 is formed of two tabs 71 and 72 with the part 71 premounted on the chamber 2. The chamber 2 is inserted into the shell 3. The second part 71 of the casing body 7 which part is preequipped with the seal 28 can therefore be inserted into the part 71 of the casing body through the orifice 6 in the shell 3.

It should be noted that, in the embodiment whereby the casing body 7 is fixed to the chamber 2 by welding, this chamber 2 is not yet positioned in the shell 3. The casing body 7 is first of all welded to the chamber 2, then the latter is slipped into the shell 3. The casing body 7 therefore positions itself in the orifice 6 of the shell 3 and provides the spacing between the two walls of the chamber 2 and of the shell 3, by means of the flange 16. This flange presses on the shell 3 from the inside.

In the case of a fitting (assembly) using a seal, the casing body 7 may be assembled with the chamber 2 after the chamber 2 has been assembled in the shell 3 as illustrated in FIG. 6 . In a variant, part of the casing body may be prefixed to the chamber 2 before the chamber 2 is assembled in the shell 3 as illustrated in FIGS. 8 and 9 . According to one particular aspect, this step of assembling the chamber 2 in the shell 3 involves injecting the insulation 15. Once the casing body 7 is in place, in the example of FIG. 6 , the flange 16 then comes to bear against the shell 3, from the outside, which is to say against that part of the external surface of the shell that surrounds the orifice 6. The separation between the two walls of the chamber 2 and of the shell 3 is therefore no longer provided by the casing body 7 but, in this way, the casing body 7 remains removable, something which would not be possible if the flange 16 were on the inside of the shell 3 as in the case of welding. In the example of FIG. 8 , the separation between the two walls of the chamber 2 and of the shell 3 is provided by the part 71 of the casing body 7. The flange 16 is on the inside of the shell 3 as in the case of welding. The part 72 of the casing remains removable so as to allow the seal 28 with which this part 72 of the casing is preequipped to be changed if necessary.

According to one embodiment, the fitting of the seal 28 may involve the following steps.

In a first step of fitting which is illustrated in FIG. 6 , the annular seal 28 is prefitted on (slipped onto) the projection 12 of the casing body 7. Its inside diameter is substantially equal to the outside diameter of the projection. Seal retention is therefore assured only by the roughness of the seal and of the projection. The seal is therefore still fairly free to move and not constrained. A small force can make it slide. The casing body 7 is not yet assembled on the chamber 2 (tank). This technique avoids the need to preposition the seal in the chamber or the tank, where access for maintenance is difficult.

The orifice 5 made in the chamber 2 is of a diameter substantially equal to the outside diameter of the annular seal 28 in the “at rest” state, namely when it is not yet constrained, and in the pre-fitted state because the seal is then not yet constrained. In a second step of fitting illustrated in FIG. 7 and corresponding to the fitting of the casing body 7 in the chamber 2, the operator first of all positions the casing body 7 to face the orifices 5 and 6 of the chamber 2 and of the shell 3 and then the operator pushes it until the rim 35 (orthogonal to the axis of the projection 12) of the annular seal 28 comes into contact with the external wall of the chamber 2. The rim 35 (which forms a flange) of the seal is then sandwiched between the external wall of the chamber 2 and the external wall of the bottom 8 of the casing body 7. The operator then continues to push on the casing body 7 so that, as the rim 35 of the seal comes into contact with the chamber 2, the seal 28 is forcibly moved onto the larger-diameter portion of the projection 12, resulting in an increase in the diameter of the seal 28. Once the casing body 7 is in position at the end of its assembly travel, its flange 16 comes to bear against the shell 3 and the annular seal 28 is constrained radially between the casing body 7 and the chamber 2 at its portion parallel to the axis of the projection 12 which forms one leg of the L of the cross section of the seal 28, the other leg of the L being formed by the rim 35.

It may be noted that, irrespective of the way in which the casing body 7 is connected to the chamber 2, the method for manufacturing such a tank 1 always comprises a step of positioning of the casing body 7 in a position in which the casing body 7 forms a connecting sleeve connecting the orifices 5, 6 of the chamber 2 and of the shell 3 to one another, this casing body 7 having a holed bottom 8 with the hole 10 in the bottom 8 of the casing body 7 being externally bordered by a rim 11 to form a tubular projection 12 that is inserted into the orifice 5 of the chamber 2 when the casing body 7 is in position in this position, and a step of positioning the resistive electrical element 13 inside the casing body 7 coaxially with the hole 10 in the bottom 8 of the casing body 7 so as to project into the chamber 2 via said hole 10, the seal 14, with which the resistive electrical element 13 is in sealed bearing contact, being considered so that in collaboration with said resistive electrical element 13 it seals the hole 10 in the bottom 8 of the casing body 7 in a fluid tight manner when the resistive electrical element 13 is in position in said hole 10 in the casing.

In order to improve said tank 1, this tank 1 is equipped with an orifice 29 for filling the tank 1 with liquid. This filling orifice 29 is equipped with a connecting piece 30 for connecting to the tank 1. This connecting piece 30 is equipped with a vent 31, with an overflow orifice 32 and with an additional orifice 33 which act as an overflow or as a vent according to the level to which the tank 1 is filled.

The vent 31, the overflow orifice 32 and the additional orifice 33 are positioned at different levels on the tank 1 and the additional orifice 33 is positioned at a level intermediate between the levels occupied by the vent 31 and the overflow orifice 32. 

1. A tank (1) for liquid comprising: a liquid receiving chamber (2), a shell (3) at least partially surrounding the chamber (2), and at least one resistive electric element (13) that can be positioned at least partially inside the chamber (2), characterized in that the tank (1) comprises, for receiving the or at least one of the electric resistive elements (13), two orifices (5, 6) facing each other, one of them, (5) being formed in the chamber (2) and the other (6) being formed in the shell (3), in that the orifices (5, 6) are connected by a casing body (7) comprising a bottom (8) and a peripheral side wall (9), in that the casing body and the chamber (2) are made of a synthetic material, in that the casing body (7), the bottom (8) of which is holed, forms a connecting sleeve connecting said orifices (5, 6) to one another, in that the hole (10) in the bottom (8) of the casing body (7) is externally bordered by a rim (11) forming a tubular projection (12) inserted into the orifice (5) of the chamber (2), and in that the resistive electrical element (13), which can be positioned inside the casing body (7) so that it is coaxial with the hole (10) in the bottom (8) of the casing body (7) in order to project into the chamber (2) via said hole (10), takes the form of an elongate body (131) fitted with a seal (14) slipped over the resistive electrical element (13), this seal (14), in fluid tight contact with the resistive electrical element (13), being configured so that it, in collaboration with the resistive electrical element (13), seals the hole (10) in the bottom (8) of the casing body (7) in a fluid tight manner when the resistive electrical element (13) is in place inserted into said hole (10).
 2. The tank (1) for liquid as claimed in claim 1, characterized in that the seal (14) takes the form of an elastically deformable block equipped with at least two through-passages (141), said block being preferably equipped with annular bulges (142) on its periphery surrounding said passages (141).
 3. The tank (1) for liquid as claimed in either of claims 1 and 2, characterized in that insulation (15) is positioned between the chamber (2) and the shell (3) and surrounds the casing body (7).
 4. The tank (1) for liquid as claimed in one of claims 1 to 3, characterized in that the peripheral side wall (9) of the casing body (7) is equipped with an external peripheral flange (16) positioned bearing against that part of the internal or external surface of the shell (3) that surrounds the hole (6) in the shell (3).
 5. The tank (1) for liquid as claimed in one of claims 1 to 4, characterized in that the tubular projection (12) of the casing body (7), which projection is inserted into the orifice (5) in the chamber (2), comprises at least one, preferably at least two thimbles (171, 172) open towards the inside of the casing body (7), each thimble (171, 172) being produced as one piece with the casing body (7).
 6. The tank (1) for liquid as claimed in claim 5, characterized in that the tank (1) comprises a temperature probe (18) that can be positioned inside the or one of the thimbles (171, 172).
 7. The tank (1) for liquid as claimed in one of claims 1 to 6, characterized in that the tank (1) comprises a fixing piece (20) for fixing the resistive electrical element (13) to the casing body (7), this fixing piece (20) being able to be slipped over the resistive electrical element (13) after the seal (14) and being able to be coupled by screw-fastening members (34) to the casing body (7), this casing body (7) comprising at least one screw-fastening well (21) produced as one piece with said body (7).
 8. The tank (1) for liquid as claimed in one of claims 1 to 7, characterized in that the orifice (6) in the shell (3) is formed in a depression (22) of the shell (3) and in that the tank (1) comprises a cap (23) for closing the casing body (7) and which is housed inside said depression (22).
 9. The tank (1) for liquid as claimed in one of claims 1 to 8, characterized in that the elongate body (131) of the or at least one of the resistive electrical elements (13) is a hairpin tubular body inside which there are housed a resistive wire (26) and at least one hot-melt component (27), the ends of the hairpin which are produced in the form of two parallel branches each being equipped with an electrical connector (24) via which the seal (14) is slipped over said branches.
 10. The tank (1) for liquid as claimed in one of claims 1 to 9, characterized in that the tank (1) is equipped with an orifice (29) for filling the tank (1) with liquid, this filling orifice (29) being equipped with a connection piece (30) for connecting to the tank (1), this connection piece (30) being fitted with a vent (31), an overflow orifice (32) and with an additional orifice (33) acting as an overflow orifice or as a vent depending on the level to which the tank (1) is filled.
 11. The tank (1) for liquid as claimed in claim 10, characterized in that, the vent (31), the overflow orifice (32) and the additional orifice (33) are positioned at different levels on the tank (1) and in that the additional orifice (33) is positioned at a level that is intermediate between the levels occupied by the vent (31) and by the overflow orifice (32).
 12. A method for manufacturing a tank (1) for liquid as claimed in one of claims 1 to 11, said liquid tank (1) comprising a liquid receiving chamber (2), a shell (3) surrounding the chamber (2) and at least one resistive electrical element (13) equipped with a seal (14) and which can be positioned at least partly inside the chamber (2), characterized in that, with the tank (1) comprising, to receive the or at least one of the resistive electrical elements (13), two orifices (5, 6) facing one another, one of them (5) formed in the chamber (2) and the other (6) in the shell (3), said method comprises a step of positioning a casing body (7) in a position in which the casing body (7) forms a connecting sleeve connecting the orifices (5, 6) of the chamber (2) and of the shell (3) to one another, the chamber (2) and the casing body (7) being made of a synthetic material, this casing body (7) having a peripheral side wall (9) and a holed bottom (8) where the hole (10) in the bottom (8) of the casing body (7) is externally bordered by a rim (11) to form a tubular projection (12) inserted into the orifice (5) in the chamber (2) when the casing body (7) is in position in said position, and a step of positioning the resistive electric element (13) inside the casing body (7) coaxial with the hole (10) in the bottom (8) of the casing body (7) so as to project via the hole (10) into the chamber (2), the seal (14), with which the resistive electrical element (13) is in bearing sealed contact, being configured so that in collaboration with said resistive electrical element (13), it seals the hole (10) in the bottom (8) of the casing body (7) in a fluid tight manner when the resistive electrical element (13) is in place inserted in said hole (10) in the casing. 